1. Field of the Invention
Embodiments of the invention generally relate a method and apparatus for etching, and more particularly, a method and apparatus suitable for etching Micro-Electro-Mechanical Systems (MEMS) devices and the like.
2. Description of the Related Art
The demand for Micro-Electro-Mechanical Systems (MEMS) devices has introduced new challenges for processing equipment companies. One challenge is providing equipment suitable for efficient plasma etching of materials utilized to fabricate MEMS structures. For example, processing equipment utilized for etching must be able to maintain good critical dimension control and mask selectivity in order to successfully manufacture MEMS structures on a commercially viable scale. Additionally for MEMS structures intended for optical devices, the processing equipment must produce sufficiently smooth sidewalls as not to inhibit obtaining performance goals.
Silicon is a material commonly used for MEMS structures. Silicon etching for MEMS fabrication is typically carried out in a reactive ion etch (RIE) reactor. Typical RIE reactors generally have limited small plasma generation areas and limited power capability. This makes it difficult to achieve good etching uniformity in larger substrate formats and also limits the etch rate. Moreover, RIE reactors generally etch faster in the center relative the edge of a substrate, which limits potential product yields and quality.
Some RIE etch reactors employ a cyclical etch process that includes several recipe steps, such as etch and deposition, or etch, flash, and deposition. The cyclical etch process may use a time multiplexed gas modulation (“TMGM”) system or a Bosch system to sequentially provide etchants and deposition species. The deposition species provides a protective film upon the previously etched surface to protect the surface, typically the sidewalls of the trench, from further etching. These two steps are repeated as a deeper and deeper trench is formed. Poor control of the cyclical etch process disadvantageously increases the roughness of the sidewalls, which may render a microelectronic device defective.
Therefore, there is a need for an improved method and apparatus of for etching.